1. Technical Field
The present invention relates to apparatus for repairing bodily tissue in vivo and has particular utilization in repairing a meniscal tear during arthroscopic surgery of the knee.
2. Discussion of the Prior Art
Although the following description is directed specifically to repairing meniscus tissue in vivo in a human knee, it should be understood that the principles of the present invention are applicable to the repair of any bodily tissue, such as cartilage, bone, skin and ligaments, in an in vivo surgical procedure.
The knee is a hinge joint which permits a limited amount of rotation. The opposing curvature of the articulating surfaces of the femur and tibia are equalized, to a certain degree, by the menisci, the wedge-shaped fibrocartilaginous structures located on the periphery of the articular surface. The menisci are mobile buffers functioning to inhibit displacement of the joint and to distribute the force exerted by the femur over a larger area of the tibia. Possible causes of damage or injury to the menisci are multiple. Damage or tear of a meniscus usually occurs when the weight-bearing joint is subjected to a combined flexion-rotation or extension-rotation motion. The elastic and fibrous structure of the menisci, the rigid fixation of the anterior and posterior attachments, and their connections with the joint capsule, cause the menisci to return to their normal positions at the periphery of the joint if there is displacement. Disturbance of the normal mechanism of the joint and interference with mobility of the menisci can exceed their elasticity and cause tears of the cartilaginous substance. This appears to occur most frequently when a meniscus that has been displaced into the joint is caught between the femoral and tibial condyles as the result of a sudden change of movement.
Treatment for torn menisci has changed considerably over the years. At one time it was advocated that a peripherally detached meniscus be removed, even though the tissue was not damaged. The rationale was that excision of the meniscus prevents meniscal re-injury in a joint in which the mechanics may have been disturbed. In many cases a complete meniscectomy (i.e., total removal of the meniscus) was performed. Results from a complete meniscectomy ultimately showed degenerative arthritis, instability and changes in the transmission of loads in the knee. Because of these complications a partial meniscectomy became an alternative to a complete meniscectomy. Recently, there has been a strong movement to save as much of the meniscus as possible, leading to the development of techniques for meniscal suturing. Animal studies have been performed to demonstrate the safety and efficiency for this procedure.
An arthrotomy, or open technique, requires large incisions to gain access to the joint. Utilizing the open technique for meniscal suturing repair provided the opportunity of returning the knee to its prior pre-injury level of performance; however, the resulting large incisions require longer periods of immobilization and consequently longer periods of rehabilitation and recovery. Recent advances in instrumentation have made it possible to repair some meniscal lesions under arthroscopic visualization. Generally, this instrumentation is for inserting and receiving the suture as it passes through the meniscus. Typically, suture is passed through the meniscal rim and body of the meniscus, guided by special cannulas through the knee. The suture is then tied posterior to the knee and placed subcutaneously. Most of these procedures are performed using a larger (i.e., four to eight centimeters) incision than the standard portals used in arthroscopy. Depending upon the meniscus to be repaired, the incision is placed on the medial or lateral side of the knee; however, because of the long needles generally employed in meniscal repair, extreme caution must be observed during this procedure in order to avoid the possibility of the needle penetrating the popliteal artery or posterior tibial nerve and catching the fat pad during passage of the needle into and out of the knee joint. A spoon-shaped instrument is generally employed to act as a needle shield or guard for the popliteal structures. Nevertheless, there have been reported instances of injury to these vital areas with consequential damage to arteries and nerve palsy in the limb. Surgical techniques are being perfected, as are improvements to instrumentation, by various groups in order to minimize these risks and to decrease the procedural time.
It is known to use certain types of metal staples in conjunction with surgery for repairing bone tissue. The legs or shafts of the staple have a series of barbs which hold the staple and surrounding base tissue in place during the healing process. Another known device serving a similar function is the Smillie nail which is a single shaft device employed for securing bone tissue parts in place during the healing process. These staple and nail devices are effective for holding the bone tissue together during healing; however, they require a second surgical procedure in order to remove the device after the tissue has healed.